Method of filling and pressurizing an aerosol can

ABSTRACT

A viscous product to be dispensed is introduced through the top opening of a can into the region of the can above a piston slidable axially within the can. A valve assembly is placed in the opening, and a vacuum is applied to a hole in the bottom of the can to draw the product against the top of the piston. Fluid pressure is then applied to the hole in the bottom of the can to move the piston and product upwardly until the product completely fills the region of the can above the piston. The hole in the bottom of the can is then plugged. During application of vacuum and fluid pressure, air is permitted to flow into and out of the top of the can either by delaying fastening of the valve assembly to the can top or by temporarily opening the valve.

United States Patent Scheindel Aug. 5, 1975 METHOD OF FILLING AND PRESSURIZING Primary ExaminerTravis S. McGehee AN AEROSOL CAN Assistant ExaminerH0race M Culver Inventor: Christian T. Scheindel, Star RL, Agen Lcvmc Randolph Center, Vt. 05061 Sept. 11, 1974 Appl No.: 504,462

ABSTRACT [22] Filed:

A viscous product to be dispensed is introduced through the top opening of a can into the region of the can above a piston slidable axially within the can A valve assembly is placed in the opening, and a vacuum 53/22 R, 22 A, 7, 8, 112 R,

is applied to a hole in the bottom of the can to draw [58] Field of Search......

the product against the top of the piston. Fluid pressure is then applied to the hole in the bottom of the can to move the piston and product upwardly until the [56] Reterences cued product completely fills the region of the can above UNITED STATES PATENTS the piston. The hole in the bottom of the can is then 3,204,387 9/1965 Scheindel.H..............,.............. 53/88 plugged. During application of vacuum and fluid pres- 3,224,l58 12/1965 Baumann 53/22 R sure, air is permitted to flow into and out of the top of 3.654.743 4/1 72 McGfiarym, 53/88 the can either by delaying fastening of the valve as- 3,827,2l2 8/1974 53/38 sembly to the can top or by temporal-y Opening the valve.

6 Claims, 7 Drawing Figures PATENTEI] AUG 5 I975 SHEET METHOD OF FILLING AND PRESSURIZING AN AEROSOL CAN This invention relates to an aerosol can of the type which houses a piston slidable along the axis of the can. Such cans have been employed for many years for dispensing viscous products such as cheese spreads and tooth paste. The product to be dispensed occupies the region of the can above the piston, and a pressurized fluid, usually air, occupies the region below the piston. When the valve at the top of the can is manipulated to open it, the pressurized fluid is able to push the piston toward the top of the can, and the piston in turn pushes some of the product out of the can through the valve.

A problem has been encountered with certain kinds of cans of this type when they are filled and stored on their sides for extended periods, i.e., of the order of several weeks. The kind of can referred to is that having a longitudinally extending seam, as contrasted with so-called seamless or deep-drawn cans. In a seamed can, the internal periphery of the can is not perfectly circular because the seam projects into the can. Consequently, although the piston is hollow and thin-walled and formed of a flexible material such as a suitable plastic, it cannot conform exactly to the internal shape of the can in the vicinity of the seam. Therefore, small spaces remain between the piston side surface and the can interior surface on each side of the seam.

Furthermore, in general practice, the product does not completely fill the can region above the piston. Specifically, the top of the piston is ordinarily shaped somewhat like a truncated cone, so that it will conform to the shape of the top of the can. Upon filling the can, air spaces usually remain between the product and the outer margin of the piston top since the product is too viscous to flow readily and fill this region. In addition, an air space is often left above the product. As a result, when the can is laid on its side for a considerable length of time, the product has an opportunity to settle into these air spaces thereby leaving a channel or air space running along the entire length of the can between the piston and the valve.

Should the can now be picked up and used, opening of the valve permits the pressurized fluid to flow from beneath the piston through the spaces between the piston side wall and the can wall on each side of the seam, through the channel alongside the product, and out through the valve. With the pressure beneath the piston thereby reduced, the ability of the piston to push the product out of the can is greatly hindered or eliminated, whereby some or all of the product can never be dispensed from the can. Any product which cannot be dispensed is of course wasted.

It is an object of the present invention to overcome this problem by providing a can filling and pressurizing method which eliminates air spaces in the region of the can above the piston, so that this region is filled completely with the product to be dispensed. As a result, even if the can is stored on its side, there is no opportunity for a channel to develop between the product and the can wall through which the fluid pressurizing the piston can escape when the valve is opened.

Additional objects and features of the invention will be apparent from the following description in which reference is made to the accompanying drawings. In the drawings:

FIG. 1 is a vertical cross-sectional view of a can housing a slidable piston immediately after a product to be dispensed has been introduced into the region of the can above the piston;

FIG. la is a horizontal cross-sectional view taken along line Ia1a of FIG. 1;

FIG. 2 is a view of the can, partially in cross-section, after a valve assembly has been placed on the can;

FIGS. 35 are views similar to FIG. I showing the sequence of steps for pressurizing and plugging the can; and

FIG. 6 is a fragmentary view similar to FIG. 3 showing an alternative step in the method.

The invention will be described in connection with a conventional three-piece can 10 comprising a cylindrical side wall 11 to the bottom edge of which a bottom wall I2 is secured in a fluid-tight manner. Bottom wall 12 is of downwardly concave shape so that it will not be bellied-out by pressure within the can. In addition, bottom wall 12 is furnished with a hole 16, the purpose of which will be seen hereinafter. A shouldershaped top wall 13 is secured in a fluid-tight manner to the upper edge of side wall II, the top wall having an opening 14 surrounded by an edge 15.

Although the invention could be used with a socalled two piece" can in which the side wall and either the top or bottom wall are formed as one piece by a deep drawing operation, it is of principal value with a three-piece can as described above. In the latter type of can, the side wall 11 is formed from initially flat stock curved into a cylindrical shape, the two meeting edges 18 and 19 (FIG. la) being welded together to form a seam 20 extending longitudinally along the can.

Within the can is a conventional shell-like piston 23 made of a suitable molded plastic, such as polyethylene. The piston is slidable axially (upwardly in FIG. 1) with respect to the can. The piston has a cylindrical side wall merging into a generally frusto-conical top wall. At its center, the top wall is formed with a depression 24 adapted to accommodate the portion 26 of a valve assembly 25 (FIG. 2) which projects into the filled can. It will be seen that the top wall of piston 23 is shaped to conform to the inner surface of the can top wall 13 and the depending valve assembly portion 26 so that when the piston reaches the top of the can it will expel all the product remaining in the can. Piston 23 is hollow and it has no bottom wall. Thus, the interior of the piston defines a space 27 adapted to accommodate a pressurized fluid.

As may beseen clearly in FIG. 1a, seam 20 projects into the can making the internal cross-sectional shape of can side wall 11 noncircular. When the space 27 within piston 23 is pressurized, the piston side wall is pressed against the inner surface of the can wall 11 to produce a snug but slidable fit. However, the piston side wall does not have sufficient flexibility to conform to the internal ridge produced by seam 20. Consequently, spaces 28 result between the piston side wall and the can side wall 11 on both sides of seam 20.

Can 20 may be filled in a completely conventional manner. Initially, piston 23 is in its lowermost position, shown in FIG. 1, wherein the lower edge of its side wall engages bottom wall 12 of the can. A filling tube 31 (shown in broken lines in FIG. I) connected through a pump to a reservoir (the last elements not being shown) of the product to be packaged is inserted into the can through opening 14. The viscous product 32 is pumped through the tube into the can, and during the flow of product out of the tube 31, the tube is retracted upwardly out of the can. When the lower end of the tube reaches the level of the lower edge of top wall 13, flow of the product stops, leaving an air space 33 in the can above the product. Furthermore, since the product is so viscous, it does not flow into contact with the entire upper surface of the top wall of piston 23, as a result of which air spaces 34 remain between the product and the outer portions of the top wall surface of piston 23.

The next step of the method (FIG. 2) involves placing a valve assembly 25 into opening 14 in the can top wall. Valve assembly 25 has a downwardly-turned lip 37 which seats upon edge surrounding opening l4. At this stage, it is preferred not to fasten lip 37 to edge 15, but to simply allow the lip to rest on the edge. As shown in FIG. 3, can 10 is then placed on a support surface 38 having a hole 39 surrounded by a ring 40 of rubber or other resilient material. The bottom circular edge of can 10 rests upon ring 40 so that the space within the can bottom edge will be sealed from the atmosphere when the can is pressed downwardly. Downward pressure on the can is provided by a cylindrical clamp 41 having openings 42 in its side wall. The top wall of clamp 41 is connected by a rod 43 to suitable means, such as an air-operated cylinder (not shown), for moving the clamp up and down as desired. The lower circular edge of clamp 41 engages top wall 13 of the can and presses it downwardly. At the same time, a source of vacuum 44, shown schematically in FIG. 3, is connected to hole 39 in support 38. The vacuum serves to draw product 32 downwardly against the top surface of piston 23 so as to completely fill air spaces 34 (FIG. 1) which were originally present immediately after the can was filled with the product. Pulling the product down on to the piston by means of vacuum applied to hole 16 is permitted only because a path has been left for air to enter the space 33 at the top of the can above the product 32. In this example, air can flow through openings 42 in the clamp and then between lip 37 and can edge 15, as indicated by the arrows in FIG. 3.

The next step of the method, shown in FIG. 4, involves clamping can 10 by a different clamp 47. Clamp 47 has a cylindrical lower portion for engaging can top wall 13, this portion being formed with openings 48, and the clamp is connected by a rod 49 to suitable means for moving it up and down. Furthermore, clamp 47 has an internal shoulder 50 which, when the clamp engages can top wall 13, is spaced just slightly above the upper surface of lip 37 of valve assembly 25. At this stage, hole 39 in support 38 is connected to a source of fluid pressure 51, shown schematically in FIG. 4, such as compressed air. Pressurized fluid flows from source 51, through hole 39 and hole 16 in the can bottom into space 27. The pressure forces piston 23 upwardly (compare FIGS. 3 and 4), the pistion in turn pushing the product upwardly until it fills the air space 33, Le, completely fills the region within the can which is above piston 23. Pushing the product up to completely fill all air spaces above it is permitted because a path for air above the product in space 33 to leave the can has been provided. As piston 23 moves upwardly, valve 6 can, as indicated by the arrows in FIG. 4, but does not leave enough of a space to permit the viscous product to leave the can.

Following the step just described with reference to FIG. 4, two additional steps are performed, as indicated in FIG. 5, each of which in itself is entirely conventional. Lip 37 of valve assembly 25 is crimped in an airtight manner around edge 15 of the can, and hole 16 in the can bottom wall 12 is closed in an airtight manner by a resilient plug 54.

This invention has been described above in connection with a package in which the can It] and valve assembly 25 are furnished separately. Certain types of cans are furnished with a valve member already permanently in place. Furthermore, for some reason it may be desirable, even when the can and valve member are furnished separately to permanently crimp the valve member in place at the time it is initially assembled with the can. In such cases, a fluid flow path at the top of the can may be provided in the manner shown in FIG. 6. In this figure, parts similar to those in FIG. 3 bear the same reference numerals. A thin blade 55 projects downwardly from the center of the top wall of clamp 41. When the clamp moves down to engage the can top wall 13, blade 55 engages the top of stem 56 of valve assembly 25 thereby opening the valve slightly so that air can flow into the can through the valve, as indicated by the arrows in FIG. 6. A similar blade can be provided on clamp 47 of FIG. 4 to open the valve just enough to allow air to escape from the can but not enough to allow the viscous product to escape through the valve.

It will be seen that by means of the present invention, the region of the can 10 above piston 23 is completely filled with the product 32, and no air spaces are left above the piston. This result is achieved not only by first applying a vacuum and then a pressurized fluid to the hole 16 in the can bottom wall 12, but by providing a flow path for air into and out of the top of the can during the application of vacuum and pressure, respectively, to the bottom of the can.

The invention has been shown and described in preferred form only, and by way of example, and many variations may be made in the invention which will still be comprised within its spirit. It is understood, therefore, that the invention is not limited to any specific form or embodiment except insofar as such limitations are included in the appended claims.

What is claimed is:

l. A method of filling and pressurizing a can having a top opening, a bottom wall formed with a hole, and a piston within the can and slidable along the axis of the can, the method comprising the steps of:

a. introducing a product to be dispensed through the top opening of the can into the region of the can above the piston,

b. placing a valve assembly into the top opening of the can,

c. applying a vacuum to the hole in the bottom of the can while permitting air to flow into the can from the top to draw the product toward the top of the piston and thereby fill any voids between the product and piston,

d. applying fluid pressure to the hole in the bottom of the can while permitting air to flow out of the top of the can to move the piston upwardly until the product completely fills the region of the can above the piston, and

e. plugging the hole in the bottom of the can.

2. A method as defined in claim 1 wherein the valve assembly is seated on the can edge surrounding the top opening but is not fastened to that edge during step (b), whereby air can flow into and out of the top of the can between said edge and the valve assembly during steps (e) and (d), respectively, and including the step of fastening the valve assembly in an air-tight manner to the can edge surrounding the top opening subsequent to step (d).

3. A method as defined in claim 2 including the step of limiting the movement of the valve assembly away from the can edge surrounding the top opening so that air is permitted to flow out of the can between that edge and the valve assembly but none of the product is permitted to flow out of the can.

4. A method as defined in claim 1 including the step of opening the valve of the valve assembly during steps (c) and (d) to permit air to flow into the can and out of the can, respectively.

5. A method as defined in claim 4 wherein the valve is opened very slightly during step (d) so as to permit air to flow through it but not to permit any of the product to flow through it.

6. A method as defined in claim 1 including the step of providing a seal between the hole in the bottom of the can and the atmosphere during steps (c) and (d). i 4 

1. A method of filling and pressurizing a can having a top opening, a bottom wall formed with a hole, and a piston within the can and slidable along the axis of the can, the method comprising the steps of: a. introducing a product to be dispensed through the top opening of the can into the region of the can above the piston, b. placing a valve assembly into the top opening of the can, c. applying a vacuum to the hole in the bottom of the can while permitting air to flow into the can from the top to draw the product toward the top of the piston and thereby fill any voids between the product and piston, d. applying fluid pressure to the hole in the bottom of the can while permitting air to flow out of the top of the can to move the piston upwardly until the product completely fills the region of the can above the piston, and e. plugging the hole in the bottom of the can.
 2. A method as defined in claim 1 wherein the valve assembly is seated on the can edge surrounding the top opening but is not fastened to that edge during step (b), whereby air can flow into and out of the top of the can between said edge and the valve assembly during steps (c) and (d), respectively, and including the step of fastening the valve assembly in an air-tight manner to the can edge surrounding the top opening subsequent to step (d).
 3. A method as defined in claim 2 including the step of limiting the movement of the valve assembly away from the can edge surrounding the top opening, so that air is permitted to flow out of the can between that edge and the valve assembly but none of the product is permitted to flow out of the can.
 4. A method as defined in claim 1 including the step of opening the valve of the valve assembly during steps (c) and (d) to permit air to flow into the can and out of the can, respectively.
 5. A method as defined in claim 4 wherein the valve is opened very slightly during step (d) so as to permit air to flow through it but not to permit any of the product to flow through it.
 6. A method as defined in claim 1 including the step of providing a seal between the hole in the bottom of the can and the atmosphere during steps (c) and (d). 